Silicon storage tubes can be used to store data such as an entire frame of a television picture or binary computer data. To store a television frame, an electronic beam is passed over the silicon coated surface and the intensity of the beam depositing the charge is varied by the video signal being stored. In an X-Y (rectangular) sweep system, a picture element occupies the same relative position on the silicon screen as it does on the television screen. Binary data can be stored and retrieved using the X and Y instantaneous sweep voltages as addresses.
It has been found that when a silicon storage tube is used to store radially swept (polar) or plan position indicator (PPI) information, the charge on the storage surface near the center where the lines converge becomes integrated. This results in the data around the center of the screen, where the sweep lines converge, being lost or erroneous. This causes a problem when storing the output signal from a PPI radar presentation on such a storage tube. The target information becomes obliterated toward the center because of the integration of charge described above.
The invention described herein is a circuit for radially sweeping a silicon storage tube and recording data thereon so that charge integration is eliminated or reduced in the area where the lines converge.